[AR] Re: Falcon 9 flight today
- From: JMKrell@xxxxxxx
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 8 Oct 2013 16:06:50 -0400 (EDT)
In a message dated 10/8/2013 10:06:43 A.M. Pacific Daylight Time,
henry@xxxxxxxxxxxxxxx writes:
On Mon, 7 Oct 2013 JMKrell@xxxxxxx wrote:
> Henry notes that most of the venting is LOX. Ionizing radiation quickly
> converts oxygen to monatomic radicals. Monatomic oxygen does etch the
> surfaces of satellites as they pass through the cloud...
Note, though, that there is plenty of atomic oxygen already present in
LEO. And it will take time for solar UV to split up many of the oxygen
molecules, time in which the cloud will be expanding rapidly. This isn't
likely to be a significant hazard.
As I stated monatomic oxygen is a nuisance and not an issue.
> The pressurizing gas in the RP-1 tanks is vented, but little RP-1.
The vapor pressure of RP-1 isn't large by Earth standards, but it's still
substantial by vacuum standards. The RP-1 won't stay in the tank,
although it may leave a bit of residue behind.
Henry, I agree with 99.9% of what you post, but on this I must go with my
empirical data. Some RP-1 is expelled during the venting of the RP-1 tank.
The rest quickly gels and solidifies within the tank. Frozen fluids under
high vacuum transfer mainly between hot and cold junctions, complicating
venting with a thermal gradient function together with the molecular pressure
function. Most of the RP-1 remains a solid until the vehicle reenters the
atmosphere. This is one reason why it has never been an issue. Are there any
molecular flow studies of vent lines?
> Venting tons of RP-1 would pose a coating hazard to satellite optics and
> sensors.
Again, this sort of thing would be an issue only if the satellite passed
very close to the venting stage, very soon after the venting started.
The density of the vapor/crystal cloud just isn't high enough to be
an issue otherwise. People vent RP-1 stages in orbit all the time; I
don't believe any satellite problem has ever been attributed to this.
Henry Spencer
henry@xxxxxxxxxxxxxxx
(hspencer@xxxxxxxxxxxxx)
(regexpguy@xxxxxxxxx)
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